Chile began a hepatitis and tetanus vaccination campaign Friday and doctors warned of outbreaks of diarrhea and infection among thousands of people displaced by the earthquake and tsunami that heavily damaged or destroyed 36 hospitals and made garbage dumps of coastal towns and cities.

With many pharmacies looted, people suffering from diabetes, hypertension and psychological illnesses are going without medicine.

Doctors report increasing cases of diarrhea among people drinking unclean water and worry that huge piles of garbage and tons of rotting fish and other debris along the coast have become nests of infection. A growing number of patients are getting injured as they wade through the mess.

"We are going to keep needing water, electric systems, a functioning sewage system. We need to clean up rotting fish in the streets. We need chemical toilets, and when it starts raining, people living in tents are going to get wet and sick. All this is going to cause infections," said Talcahuano Mayor Gaston Saavedra, whose port city was heavily damaged Feb. 27 by the quake and tsunami.

Chile said more than a dozen of its military and civilian field hospitals were operating Friday. Mobile hospitals from a half dozen other countries also were opening or about to open - an unusual situation for a country that proudly sends rescue and relief teams to the world's trouble spots.

But most of the foreign units weren't treating anyone a week after the disaster. Chile insisted that donor nations first figure out how to coordinate with Chile's advanced, if wounded, public health system.

Field hospitals being provided by Argentina, Brazil, Cuba, Peru, Spain and the United States are meant to relieve 36 heavily damaged or destroyed Chilean hospitals, including Santiago's now-closed 522-bed Felix Bulnes Hospital. Powerful aftershocks Friday forced the evacuation of an older wing of Concepcion's five-story regional hospital.

The most powerful aftershock in six days sent terrified Chileans fleeing into the streets and forced doctors to evacuate some patients from the regional hospital. The magnitude-6.6 shock at 8:47 a.m. rattled buildings for nearly a minute and sent office chairs spilling from an exposed upper floor of a badly damaged 22-story office building.

Housing Minister Patricia Poblete said that at least 500,000 homes were destroyed but that she expected that figure to reach as high as 1.5 million once surveys are complete. Disaster officials announced they had double-counted at least 271 missing as dead - an error that would drop the official death toll to about 540 without other mistakes. Interior Department officials said they would now release only the number of dead who had been identified: 452 as of late Friday.